diff --git a/libraries/AC_AttitudeControl/AC_AttitudeControl_Heli.h b/libraries/AC_AttitudeControl/AC_AttitudeControl_Heli.h
index 183c4f7cf2..c905e6896d 100644
--- a/libraries/AC_AttitudeControl/AC_AttitudeControl_Heli.h
+++ b/libraries/AC_AttitudeControl/AC_AttitudeControl_Heli.h
@@ -7,6 +7,7 @@
 #define AC_ATTITUDECONTROL_HELI_H
 
 #include <AC_AttitudeControl.h>
+#include <AP_MotorsHeli.h>
 #include <AC_HELI_PID.h>
 #include <Filter.h>